The Vatican confirmed the trip on Friday, saying Francis would visit Vilnius and Kaunas in Lithuania, Riga and Aglona in Latvia, and Tallinn in Estonia.
Lithuania has the largest Catholic community in the Baltics, accounting for more than 75% of the nation's nearly three million inhabitants.
The three Baltic nations declared their independence from Russia in 1918 but were incorporated into the Soviet Union in 1940 and remained part of it until 1991.
Francis has only one other confirmed trip for the rest of 2018, to Geneva in June.
He is widely expected to go to Ireland in August for the World Meeting of Families.
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